(Above) [Picture of a sculpture, made of sodium acetate+water solution.]
Plan/Hypothesis
We planned to make a pocket hand warmer, but due to the lack of time, we changed our mind to make a hot ice instead, which is actually the same thing except the process of sealing. We decided to use sodium acetate beacuse it was easy to afford and non-toxic, unlike the solid ones using the rusting process of metal. Being specific for the hypothesis, we thought it'll be better to dissolve more sodium acetate into the water to make supersaturation better, which means 'faster' and more 'succeessive.'
Apparatus
1.100ml of water
2. Sodium acetate powder
3. 1 beaker
4. 1 heater
5. 1 stirring rod
6. 1 extra case (to make a hot ice)
+ADDITIONAL [to make a hand warmer]
7. Lighter
8. Invincible pack (which doesn't melt under a certain amount heat)
9. A piece of metal
Procedure
>>[Steps introduced as video]
1. Pour 100ml of water into the pan
2. Heat the water until it is almost boiling
3. Put little sodium acetate into the water, and stir it until it is completely dissolved.
4. Keep repeating step 3 until sodium acetate poweder can't be dissolved anymore.
5. Remove the remaining powder in the solution and cool it down in the fridge.
6. Pour the solution in another case (optional)
7. Gently touch on the surface of the solution to create a seed crystal
8. Watch what happens!
9. In order to make the solution into the liquid form again,
+ADDITIONAL [to make a hand warmer]
10. Stuff the solution and the metal piece inside the vinyl pack
11. Seal the pack with lighter (DONE)
12. Bend the metal piece several times, and the crystalization process will begin again,
and you'll get heat
13. In order to reuse, put the hand warmer inside hot water and melt down the solutions.
14. Reuse it. (12-14 continued)
Explanation
>[picture of the sodium acetate solution crystalizing, around the seed crystal]
Firstly, pour 100ml of water into a beaker and heat it until it is almost boiling. You need to almost boil it because the water will evaporate and will not able to contain the certain amount of sodium acetate which makes the water supersaturated with it. If the water becomes around 70 degrees Celsius, start putting in the sodium acetate until it is completely dissolved. You can identify whether it is completely supersaturated or not by stirring. If you start to feel something solid is keep remaining inside the beaker, than stop putting more sodium acetate in the beaker. Actually there is a precise measurement; you need to put 37 grams of sodium acetate per 100ml of water in order to make it saturated, but according to our experiment 37 grams weren’t enough to make a perfect hot ice. So it is preferred to add as much as you can. After supersaturating the solution, remove all the powders and cool it down in the fridge. However do not leave in the fridge too long or else it’ll not work. After cooling down, gently touch on its surface to see the crystallization process-and if you want to un-crystallize it, add enough heat.
water+beaker = 179.18 g
water+beaker+sodium acetate = 263.12 g
Water = 1g/ml
Sodium Acetate = 83.94
Observation & Results
We tried three times for this experiment. However, they all turned out to be failures. First trial failed because we couldn't identify how much sodium acetate is needed to supersaturate the solution, so we added too less (app. 30.00 gm). Second trial, on the other hand, we put too much sodium acetate (83.94gm), and it made its crystalization process in the fridge, while cooling down. If we could adjust the perfect amount of sodium acetate per 100ml of water, the experiment might have ended up as a success - Actually the last trial was almost a success, but it took too much time for the solution to solidify, unlike the hand warmers at markets or the hot ice on youtube (and we think, it is because we didn't cool it down enough).
What we observed after solidifying (crystalizing) sodium acetate is that it looks like a piece of dried ice, but hot instead. It still had its own acidic smell also, and it was smoother than the original ice. However the most significant observation is that it was hot, due to the heat released from the crystalization process of the sodium acetate molecules.
Information & Evaluation
Supersaturation
Supersaturation means containing more amount of solute in the soluvent than it can dissolve. In other words, the solvent has extra solute even after it is completely saturated. Supersaturated substances are usually very unstable, and become easily crystalized if any stimulation had acted on.
Sodium acetate
1. Chemical Formula: CH3COONa 3H2O
>>>[Sodium Acetate Trihydrate molecular model]
2. Solubility: 76 gm/100ml water at 100C
>This is why we failed on the first trial. It should be at least 76g in order to make a supersaturated solution!
3. It is inexpensive and easy to afford, due to its easy creation method and popularity.
>This is the reason why sodium acetate is widely used to make a hand warmer
4. It contains a lot of heat during the process of supersaturation. For other substances, it is usual to give off heat at start solidifying if the temperature goes down to a certain degree, but sodium acetate isn't. However, even though it doens't solidify easily, it remains very unstable. This unstable susbtance starts to solidify and give off heat when a little piece of sodium acetate solution or any substance which can act as a seed crystal.
>How it becomes solid/releases heat
5. As the seed crystal formed, the crystalization begins. The solution begins to solidify around the seed crystal, which will show up like the picture below (to be attached). Crystalization occurs because every substance tries to be 'stable' rather than remaining 'unstable.'
>Reason why stimulation has to be added to the solution to become solid
6. Using this process, it is able to create a reusable hand warmer, packing the sodium acetate solution and giving a gentle stimulation and starting off crystalizing with a seed crystal.
7. When heat is added to the crystalized solution, sodium acetate absorbs heat and becomes a liquid form again.
>Reason why it is "REUSABLE"
Reflection
Being very definite, the experiment was a total failure. We made 3 trials, and nothing actually succeed to act like a hot ice, because they were too watery or contained too less amount of sodium acetate. In addition, even though we aimed to make a hand warmer, we ended up just making a failed hot ice due to the lack of time and our misunderstanding on the concept of supersaturation. However, I still think it was a very precious experience because it helped me to understand better about the idea of supersaturation. In addition, I always wondered how reusable hand warmers work and are reusable, and this experiment helped me to solve those questions. I would like to recommend this experiment to later students because the experiment is very scientific and easy- and they will feel very commendable to theirselves if the experement ends up as a success.
Table of Contents
Making A Pocket HOT ICE/HAND WARMER
(Above) [Picture of a sculpture, made of sodium acetate+water solution.]
Plan/Hypothesis
We planned to make a pocket hand warmer, but due to the lack of time, we changed our mind to make a hot ice instead, which is actually the same thing except the process of sealing. We decided to use sodium acetate beacuse it was easy to afford and non-toxic, unlike the solid ones using the rusting process of metal. Being specific for the hypothesis, we thought it'll be better to dissolve more sodium acetate into the water to make supersaturation better, which means 'faster' and more 'succeessive.'Apparatus
1.100ml of water2. Sodium acetate powder
3. 1 beaker
4. 1 heater
5. 1 stirring rod
6. 1 extra case (to make a hot ice)
+ADDITIONAL [to make a hand warmer]
7. Lighter
8. Invincible pack (which doesn't melt under a certain amount heat)
9. A piece of metal
Procedure
>>[Steps introduced as video]
1. Pour 100ml of water into the pan
2. Heat the water until it is almost boiling
3. Put little sodium acetate into the water, and stir it until it is completely dissolved.
4. Keep repeating step 3 until sodium acetate poweder can't be dissolved anymore.
5. Remove the remaining powder in the solution and cool it down in the fridge.
6. Pour the solution in another case (optional)
7. Gently touch on the surface of the solution to create a seed crystal
8. Watch what happens!
9. In order to make the solution into the liquid form again,
+ADDITIONAL [to make a hand warmer]
10. Stuff the solution and the metal piece inside the vinyl pack
11. Seal the pack with lighter (DONE)
12. Bend the metal piece several times, and the crystalization process will begin again,
and you'll get heat
13. In order to reuse, put the hand warmer inside hot water and melt down the solutions.
14. Reuse it. (12-14 continued)
Explanation
>[picture of the sodium acetate solution crystalizing, around the seed crystal]
Firstly, pour 100ml of water into a beaker and heat it until it is almost boiling. You need to almost boil it because the water will evaporate and will not able to contain the certain amount of sodium acetate which makes the water supersaturated with it. If the water becomes around 70 degrees Celsius, start putting in the sodium acetate until it is completely dissolved. You can identify whether it is completely supersaturated or not by stirring. If you start to feel something solid is keep remaining inside the beaker, than stop putting more sodium acetate in the beaker. Actually there is a precise measurement; you need to put 37 grams of sodium acetate per 100ml of water in order to make it saturated, but according to our experiment 37 grams weren’t enough to make a perfect hot ice. So it is preferred to add as much as you can. After supersaturating the solution, remove all the powders and cool it down in the fridge. However do not leave in the fridge too long or else it’ll not work. After cooling down, gently touch on its surface to see the crystallization process-and if you want to un-crystallize it, add enough heat.
water+beaker = 179.18 g
water+beaker+sodium acetate = 263.12 g
Water = 1g/ml
Sodium Acetate = 83.94
Observation & Results
We tried three times for this experiment. However, they all turned out to be failures. First trial failed because we couldn't identify how much sodium acetate is needed to supersaturate the solution, so we added too less (app. 30.00 gm). Second trial, on the other hand, we put too much sodium acetate (83.94gm), and it made its crystalization process in the fridge, while cooling down. If we could adjust the perfect amount of sodium acetate per 100ml of water, the experiment might have ended up as a success - Actually the last trial was almost a success, but it took too much time for the solution to solidify, unlike the hand warmers at markets or the hot ice on youtube (and we think, it is because we didn't cool it down enough).What we observed after solidifying (crystalizing) sodium acetate is that it looks like a piece of dried ice, but hot instead. It still had its own acidic smell also, and it was smoother than the original ice. However the most significant observation is that it was hot, due to the heat released from the crystalization process of the sodium acetate molecules.
Information & Evaluation
Supersaturation
Supersaturation means containing more amount of solute in the soluvent than it can dissolve. In other words, the solvent has extra solute even after it is completely saturated. Supersaturated substances are usually very unstable, and become easily crystalized if any stimulation had acted on.
Sodium acetate
1. Chemical Formula: CH3COONa 3H2O
>>>[Sodium Acetate Trihydrate molecular model]
2. Solubility: 76 gm/100ml water at 100C
>This is why we failed on the first trial. It should be at least 76g in order to make a supersaturated solution!
3. It is inexpensive and easy to afford, due to its easy creation method and popularity.
>This is the reason why sodium acetate is widely used to make a hand warmer
4. It contains a lot of heat during the process of supersaturation. For other substances, it is usual to give off heat at start solidifying if the temperature goes down to a certain degree, but sodium acetate isn't. However, even though it doens't solidify easily, it remains very unstable. This unstable susbtance starts to solidify and give off heat when a little piece of sodium acetate solution or any substance which can act as a seed crystal.
>How it becomes solid/releases heat
5. As the seed crystal formed, the crystalization begins. The solution begins to solidify around the seed crystal, which will show up like the picture below (to be attached). Crystalization occurs because every substance tries to be 'stable' rather than remaining 'unstable.'
>Reason why stimulation has to be added to the solution to become solid
6. Using this process, it is able to create a reusable hand warmer, packing the sodium acetate solution and giving a gentle stimulation and starting off crystalizing with a seed crystal.
7. When heat is added to the crystalized solution, sodium acetate absorbs heat and becomes a liquid form again.
>Reason why it is "REUSABLE"
Reflection
Being very definite, the experiment was a total failure. We made 3 trials, and nothing actually succeed to act like a hot ice, because they were too watery or contained too less amount of sodium acetate. In addition, even though we aimed to make a hand warmer, we ended up just making a failed hot ice due to the lack of time and our misunderstanding on the concept of supersaturation. However, I still think it was a very precious experience because it helped me to understand better about the idea of supersaturation. In addition, I always wondered how reusable hand warmers work and are reusable, and this experiment helped me to solve those questions. I would like to recommend this experiment to later students because the experiment is very scientific and easy- and they will feel very commendable to theirselves if the experement ends up as a success.Info From:
http://www.math.mtu.edu/gk-12/supersaturation.html
http://www.jtbaker.com/msds/englishhtml/s2666.htm
http://jchemed.chem.wisc.edu/JCeSoft/CCA/CCA3/MAIN/ACETATE/PAGE1.HTM
http://en.wikipedia.org/wiki/Sodium_acetate
Images from Google.com